This invention relates to fluid brake control systems for railroad vehicles and it more particularly relates to a combined triple valve and proportioning valve device for such a system.
It is known in a prior McEathron U.S. Pat. No. 4,127,308, granted Nov. 18, 1978 and in a prior Hart U.S. Pat. No. 4,188,071, granted Feb. 12, 1980, as well as in a prior Engle U.S. application Ser. No. 776,763, filed Sept. 16, 1985, which has resulted in U.S. Pat. No. 4,653,812, granted Mar. 31, 1987, that considerably smaller emergency and auxiliary reservoirs are rerquired if, for an emergency brake application, a brake cylinder is charged first to service brake presure from the auxiliary reservoir, and then from the emergency reservoir to emergency brake pressure, without equalizing the emergency and auxiliary reservoir pressures. This mode of operation is provided according to the prior art by the use of separate and independent emergency equalizing, and triple valves.
An object of the present invention is to provide the fluid brake control system which substantially obviates one or more of the limitations and disadvantages of the described prior systems.
Another object of the present invention is to reduce the number of separate valves required by combining the emergency equalizing valve and the triple valve into a single control valve device.
Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawing and in part pointed out as the description of the invention progreses.